EP4189144A1 - Porous electrolyzer gas diffusion layer and method of making thereof - Google Patents
Porous electrolyzer gas diffusion layer and method of making thereofInfo
- Publication number
- EP4189144A1 EP4189144A1 EP21851336.4A EP21851336A EP4189144A1 EP 4189144 A1 EP4189144 A1 EP 4189144A1 EP 21851336 A EP21851336 A EP 21851336A EP 4189144 A1 EP4189144 A1 EP 4189144A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- porous titanium
- sheet
- titanium sheet
- titanium
- porous
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000009792 diffusion process Methods 0.000 title claims abstract description 63
- 238000004519 manufacturing process Methods 0.000 title description 7
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 209
- 239000010936 titanium Substances 0.000 claims abstract description 179
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 176
- 239000000843 powder Substances 0.000 claims abstract description 57
- 238000000034 method Methods 0.000 claims abstract description 40
- 238000010345 tape casting Methods 0.000 claims abstract description 14
- 239000012528 membrane Substances 0.000 claims abstract description 9
- 239000007789 gas Substances 0.000 claims description 66
- 238000005245 sintering Methods 0.000 claims description 38
- 239000000314 lubricant Substances 0.000 claims description 30
- 239000000463 material Substances 0.000 claims description 29
- 239000000203 mixture Substances 0.000 claims description 27
- 239000011148 porous material Substances 0.000 claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 23
- 238000000576 coating method Methods 0.000 claims description 20
- 239000011248 coating agent Substances 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 13
- 239000002245 particle Substances 0.000 claims description 12
- 239000003792 electrolyte Substances 0.000 claims description 11
- -1 titanium hydride Chemical compound 0.000 claims description 11
- 238000005520 cutting process Methods 0.000 claims description 10
- 229910000048 titanium hydride Inorganic materials 0.000 claims description 10
- 229910001069 Ti alloy Inorganic materials 0.000 claims description 7
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 claims description 7
- 239000011230 binding agent Substances 0.000 claims description 6
- 239000004014 plasticizer Substances 0.000 claims description 5
- 239000002904 solvent Substances 0.000 claims description 5
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 4
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 239000011733 molybdenum Substances 0.000 claims description 4
- 229910052758 niobium Inorganic materials 0.000 claims description 4
- 239000010955 niobium Substances 0.000 claims description 4
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 4
- 229910052715 tantalum Inorganic materials 0.000 claims description 4
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 4
- 229910052726 zirconium Inorganic materials 0.000 claims description 4
- 238000009826 distribution Methods 0.000 claims description 3
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 3
- 239000005518 polymer electrolyte Substances 0.000 claims description 3
- 230000002902 bimodal effect Effects 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 238000004663 powder metallurgy Methods 0.000 abstract description 10
- 229910000510 noble metal Inorganic materials 0.000 description 21
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 13
- 239000001301 oxygen Substances 0.000 description 13
- 229910052760 oxygen Inorganic materials 0.000 description 13
- 230000008569 process Effects 0.000 description 11
- 239000012071 phase Substances 0.000 description 9
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 9
- 229910021332 silicide Inorganic materials 0.000 description 9
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical compound [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 description 9
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 8
- 238000005260 corrosion Methods 0.000 description 8
- 230000007797 corrosion Effects 0.000 description 8
- 229910052710 silicon Inorganic materials 0.000 description 7
- 239000010703 silicon Substances 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 229910052737 gold Inorganic materials 0.000 description 5
- 239000010931 gold Substances 0.000 description 5
- 239000011261 inert gas Substances 0.000 description 5
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 4
- 238000005056 compaction Methods 0.000 description 4
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 4
- 239000001257 hydrogen Substances 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 229910052697 platinum Inorganic materials 0.000 description 4
- 238000011144 upstream manufacturing Methods 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 239000003112 inhibitor Substances 0.000 description 3
- 229910052756 noble gas Inorganic materials 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
- 229910001220 stainless steel Inorganic materials 0.000 description 3
- 229910021341 titanium silicide Inorganic materials 0.000 description 3
- 230000032258 transport Effects 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 238000007792 addition Methods 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 238000000137 annealing Methods 0.000 description 2
- 238000004049 embossing Methods 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 230000001965 increasing effect Effects 0.000 description 2
- 229910052741 iridium Inorganic materials 0.000 description 2
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 2
- 239000004417 polycarbonate Substances 0.000 description 2
- 239000004926 polymethyl methacrylate Substances 0.000 description 2
- 229920000379 polypropylene carbonate Polymers 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 229920000557 Nafion® Polymers 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229910001423 beryllium ion Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000012799 electrically-conductive coating Substances 0.000 description 1
- 239000010411 electrocatalyst Substances 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910001092 metal group alloy Inorganic materials 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 238000000059 patterning Methods 0.000 description 1
- 238000005240 physical vapour deposition Methods 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920005597 polymer membrane Polymers 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000004151 rapid thermal annealing Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 239000010948 rhodium Substances 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 238000007788 roughening Methods 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 150000003609 titanium compounds Chemical class 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- 235000012773 waffles Nutrition 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
- B22F5/006—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of flat products, e.g. sheets
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/11—Making porous workpieces or articles
- B22F3/1103—Making porous workpieces or articles with particular physical characteristics
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/11—Making porous workpieces or articles
- B22F3/1103—Making porous workpieces or articles with particular physical characteristics
- B22F3/1109—Inhomogenous pore distribution
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/12—Both compacting and sintering
- B22F3/16—Both compacting and sintering in successive or repeated steps
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
- B22F7/002—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of porous nature
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
- B22F7/008—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression characterised by the composition
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/02—Hydrogen or oxygen
- C25B1/04—Hydrogen or oxygen by electrolysis of water
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B13/00—Diaphragms; Spacing elements
- C25B13/02—Diaphragms; Spacing elements characterised by shape or form
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B13/00—Diaphragms; Spacing elements
- C25B13/04—Diaphragms; Spacing elements characterised by the material
- C25B13/05—Diaphragms; Spacing elements characterised by the material based on inorganic materials
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
- C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
- C25B9/23—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms comprising ion-exchange membranes in or on which electrode material is embedded
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/60—Constructional parts of cells
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
- B22F2003/241—Chemical after-treatment on the surface
- B22F2003/242—Coating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2201/00—Treatment under specific atmosphere
- B22F2201/02—Nitrogen
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2301/00—Metallic composition of the powder or its coating
- B22F2301/20—Refractory metals
- B22F2301/205—Titanium, zirconium or hafnium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2302/00—Metal Compound, non-Metallic compound or non-metal composition of the powder or its coating
- B22F2302/20—Nitride
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
- B22F2998/10—Processes characterised by the sequence of their steps
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
Definitions
- PEM POROUS ELECTROLYZER GAS DIFFUSION LAYER AND METHOD OF MAKING THEREOF Cross-Reference To Related Applications
- a porous titanium sheet configured to function as an anode side gas diffusion layer of a proton exchange membrane (PEM) electrolyzer is formed by a powder technique.
- a method comprises making a porous titanium sheet configured to function as an anode side gas diffusion layer of a proton exchange membrane (PEM) electrolyzer by a powder technique.
- Figures Figure 1 is a perspective cut-away view of a PEM electrolyzer.
- Figures 2A – 2F are side cross sectional views of steps in a powder metallurgy method of making a gas diffusion layer for a PEM electrolyzer.
- Figure 3 is a perspective view of a gas diffusion layer according to an embodiment of the present disclosure.
- Figures 4 and 5 are another perspective views of a gas diffusion layer according to embodiments of the present disclosure.
- Figure 6 is side cross sectional view of a tape casting apparatus which may be used to form a gas diffusion layer according to embodiments of the present disclosure.
- Figure 1 illustrates a perspective cut-away view of a PEM electrolyzer that is described in an article by Greig Chisholm et al. “3D printed flow plates for the electrolysis of water: An economic and adaptable approach to device manufacture” Energy Environ. Sci., 2014, 7, 3026–3032.
- the PEM electrolyzer 1 includes an anode side flow plate 2 and cathode side flow plate 4 with fluid flow channels 6 and respective openings 8, 9, 10, a PEM polymer electrolyte 12 located between the flow plates 2, 4, an anode side gas diffusion layer 14 located between the electrolyte 12 and the anode side flow plate 2, an anode electrode 16 located between the anode side gas diffusion layer 14 and the electrolyte 12, a cathode side gas diffusion layer 18 located between the electrolyte 12 and the cathode side flow plate 4, and a cathode electrode 20 located between the cathode side gas diffusion layer 18 and the electrolyte 12.
- the anode side flow plate 2 may include a water inlet opening 8, an oxygen outlet opening 9 and a water flow channel (e.g. tortuous path groove) 6 connecting the water inlet opening 8 and the oxygen outlet opening 9 in the side of the flow plate 2 facing the anode side gas diffusion layer 14.
- the anode side gas diffusion layer 14 may comprise a porous titanium layer.
- the cathode side gas diffusion layer 18 may comprise a porous carbon layer.
- the anode electrode 16 may comprise any suitable anode catalyst, such as an iridium layer.
- the cathode electrode 20 may comprise any suitable cathode catalyst, such as a platinum layer. Other noble metal catalyst layers may also be used for the anode and/or cathode electrodes.
- the electrolyte 12 may comprise any suitable proton exchange (e.g., hydrogen ion transport) polymer membrane, such as a Nafion® membrane composed of sulfonated tetrafluoroethylene based fluoropolymer-copolymer having a formula C 7 HF 13 O 5 S . C 2 F 4 .
- a suitable proton exchange (e.g., hydrogen ion transport) polymer membrane such as a Nafion® membrane composed of sulfonated tetrafluoroethylene based fluoropolymer-copolymer having a formula C 7 HF 13 O 5 S . C 2 F 4 .
- water is provided into the water flow channel 6 through the water inlet opening 8.
- the water flows through the water flow channel 6 and through the anode side gas diffusion layer 14 to the anode electrode 16.
- the water is electrochemically separated into oxygen and hydrogen at the anode electrode 16 upon an application of an external current or voltage between the anode electrode 16 and
- a porous titanium layer (e.g., sheet) may be used as the anode side gas diffusion layer (i.e., transport layer) 14.
- the porous titanium layer (e.g., sheet) that is used as an anode side gas diffusion layer 14 is formed by a powder process.
- the powder process comprises tape casting.
- the porous titanium sheet After the porous titanium sheet is sintered, it may be coated on both sides (e.g., on the anode electrode side and the flow plate side) with a conductivity enhancing and/or corrosion resistant coating, such as a platinum and/or gold coating to provide good conductivity and corrosion resistance.
- the coating may be formed by physical vapor deposition, such as evaporation.
- the porous titanium layer (e.g., sheet) that is used as an anode side gas diffusion layer 14 is formed by a powder metallurgical technique, in which a titanium powder is pressed into a porous titanium sheet using compaction process. The compacted sheet is then sintered to yield a gas diffusion layer (e.g., sheet) with an established metallurgical bond.
- the porous titanium sheet may have a porosity between 40 and 60 percent.
- the powder metallurgy press apparatus 100 includes a chamber 101 containing an upper punch 102 and a lower punch 104 that move axially relative to a die cavity 106 located in a die 108.
- the steps in the powder metallurgy compaction cycle include lowering the lower punch 104 from the elevated position to expose the die cavity 106, as shown in Figures 2A and 2B.
- the titanium powder 112 is mixed with a lubricant and then provided into a powder shoe 110.
- the powder shoe 110 containing the titanium powder 112 mixed with the lubricant moves over the die cavity to fill the die cavity with a mixture of titanium powder 112 and lubricant.
- the top and/or bottom punches 102, 104 move relative to the die 108 to compress the titanium powder 112, as shown in Figures 2C and 2D.
- the top punch 102 is retracted upwards and the bottom punch 104 moves relative to the die 108 to eject the compacted green titanium sheet 114 from the die cavity 106, as shown in Figure 2E.
- the shoe 110 then again moves across the top surface of the die 108 where it refills the die cavity with additional titanium powder 112 and lubricant mixture and pushes the green titanium sheet 114 out of the die 108, as shown in Figure 2F.
- the green titanium sheet 114 may be provided onto a moving belt which moves the green titanium sheet through one or more belt furnaces.
- the sheet may first be annealed at a lower temperature in a de-binding process to burn out the organic lubricant (i.e., binder), followed by annealing at a high temperature to sinter the de-lubricated titanium sheet.
- the sintered porous titanium sheet 14 is then provided into the electrolyzer (e.g., the electrolyzer 1 of Figure 1) between the anode side flow plate 2 and the membrane – electrode assembly (i.e., the electrolyte 12 with anode electrode 16 and cathode electrode 20 located on opposite sides thereof) to function as the anode side gas diffusion layer 14.
- a first major side 14A of the porous titanium sheet 14 has a higher porosity than an opposite second major side 14B of the porous titanium sheet 14.
- the first major side 14A of the porous titanium sheet 14 faces the anode side flow plate 2, and the opposite second major side 14B of the porous titanium sheet 14 faces the anode electrode 16.
- the first major side 14A of the porous titanium 14 sheet may have the porosity which is at least 10 percent higher than the opposite second major side 14B of the porous titanium sheet 14.
- the first major side 14A of the porous titanium sheet may have a porosity of 40 to 50%, while the opposite second major side 14B of the porous titanium sheet may have a porosity of 50 to 60%.
- the higher porosity on the flow plate 2 side 14A of the porous titanium sheet 14 permits more water to enter the pores, while the lower porosity on the anode electrode 16 side 14B of the titanium sheet 14 provides an improved electrical contact with the anode electrode 16.
- the porosity difference may be a continuous porosity gradient in which the porosity increases continuously from the first major side 14A to the second major side 14B (i.e. between opposing major surfaces).
- the porosity may change in a stepwise fashion such that the porous titanium sheet 14 has at least first and second portions (14A, 14B) having different respective porosities from each other.
- a different amount of lubricant is added to top and bottom sections of the titanium powder 112 in the die cavity 106 in a continuous gradient or in a stepwise manner.
- the porous titanium sheet 14 has a higher porosity in a portion 14A that is made from a powder section containing a higher lubricant concentration than in a portion 14B that is made from a powder section containing a lower lubricant concentration.
- the different lubricant concentration in the die cavity 106 may be formed by two or more different passes of the shoe 110 in which the titanium powder 112 to lubricant ratio is different (e.g., higher or lower) in different passes.
- the die cavity 106 is partially filled during the first shoe 110 pass with a first portion of the mixture of the titanium powder 112 and lubricant having a first titanium powder to lubricant ratio, and the die cavity 106 is additionally filled during the second shoe 110 pass with a second portion of the mixture of the titanium powder 112 and lubricant having a second titanium powder to lubricant ratio different from the first ratio.
- the lower titanium powder 112 to lubricant ratio results in a higher porosity during the de-binding anneal step.
- a first major surface of the anode side flow plate which faces the anode side gas diffusion layer 14 contains a water flow channel groove 6, as shown in Figure 1.
- the first major side 14A of the porous titanium sheet 14 which faces the anode side flow plate 2 includes a groove 26 which is a substantial mirror image of the water flow channel groove 6, as shown in Figure 3.
- a substantial mirror image of the water flow channel groove 26 means a shape which is a general mirror image of the water flow channel groove 6, but which may have dimensions which differ by less than 20%.
- an opposite second major side 14B of the porous titanium sheet 14 which faces the anode electrode 16 has a substantially planar surface which lacks a groove 26.
- Such design facilitates water flow on the flow plate 2 side 14A of the gas diffusion later 14, while maintaining a good electrical contact between the gas diffusion layer 14 and the anode electrode 16.
- the groove 26 in the porous titanium sheet 14 may be formed by using the upper punch 102 or the lower punch 104 in the apparatus of FIG.2A which contains a protrusion which is a mirror image of the groove 26.
- the porous titanium sheet 14 has a bimodal distribution of pore sizes as part of the porosity network.
- the two modes of the pore sizes are broadly classified as micropores 15B and macropores 15A which are larger than the micropores 15B.
- Micropores 15B act as capillary tubes and help transport water from the groove 6 to the anode electrode (e.g., anode catalyst layer) 16, while the macropores 15A provide low flow resistive path for generated gas to leave electrocatalyst to the grove 6 to be transported by the flowing water. Pore sizes may be calculated using Young Laplace equation. In one embodiment, the micropore 15B average pore size is in the range of 1 to 5 microns and the macropore 15A average pore size is in the range of 30 to 40 microns.
- the porous titanium sheet 14 formation in the powder press apparatus 100 of Figures 2A – 2F is carried out in an inert, low oxygen partial pressure atmosphere in the chamber 101 so that titanium is not oxidized to titanium dioxide to reduce resistive losses and avoid a fire due to titanium oxidation.
- the inert atmosphere may comprise any suitable inert gas, such as a noble gas, such as argon.
- the atmosphere may comprise an oxygen partial pressure of less than 0.1 atm, such as 0.0001 to 0.01 atm.
- the inert gas may be provided into the chamber 101 containing the die 108 and the punches 102, 104. Alternatively the inert gas may be provided into the die cavity as a gas blanket from an inert gas conduit after filling the die cavity with the titanium powder.
- the porous titanium sheet 14 formation in the powder press apparatus 100 of Figures 2A – 2F is carried out with titanium alloy powders.
- Titanium may be alloyed with any one or more of molybdenum, vanadium, niobium, tantalum, and/or zirconium.
- a titanium alloy powder containing more than 50 atomic percent titanium e.g., 60 to 99 atomic percent Ti and less than 50 atomic percent, such as 1 to 40 atomic percent molybdenum, vanadium, niobium, tantalum, and/or zirconium
- the powder particles comprise the titanium alloy particles.
- a combination (e.g., mixture) of two powders may be used in the powder press apparatus: a titanium containing powder, such as a pure titanium powder, and an alloying element powder containing molybdenum, vanadium, niobium, tantalum, and/or zirconium.
- the combination of the powders contains more than 50 atomic percent titanium powder particles (e.g., 60 to 99 atomic percent Ti) and less than 50 atomic percent, such as 1 to 40 atomic percent of the alloying element powder particles.
- the porous titanium alloy sheet is formed during compaction in the powder press apparatus.
- the combination of chemical stability requirements and the processability requirements may be used to select the grade of titanium alloy.
- the alloy grades can be Grades 1, 2, 3, 6, 7, 9, 11, 16, 17,18, 21, 24, 26, 27, 29, 32, 36 and/or 37.
- a noble metal coating e.g., gold or platinum group metal coating
- a noble metal powder is provided into the die cavity 106 below and above the titanium powder 112, following by compressing all powders together using the punches 102, 104, as shown in Figures 2A – 2F.
- the different powder layers may be formed by three or more different passes of the shoe 110 in which the powder composition varies in different passes.
- the die cavity 106 is partially filled during the first shoe pass with a noble metal powder and lubricant mixture, then the die cavity is additionally filled with a titanium powder 112 and lubricant mixture during the second shoe pass, and finally the die cavity is filled with a noble metal powder and lubricant mixture during the third shoe pass.
- two different shoes 110 filled with different powder may be used.
- a first shoe filled with the noble metal powder and lubricant mixture is used during the first and the third shoe passes.
- a different second shoe filled with the titanium powder and lubricant mixture is used during the second shoe pass. This forms a noble metal / titanium / noble metal powder tri-layer in the die cavity. The tri-layer is then compressed to form a porous titanium plate coated on both major surfaces by a noble metal.
- the porous titanium sheet has inherent vias that are filled in with one or more noble metal powder to create highly conductive vias 22.
- the porous titanium or titanium alloy sheet 14 includes noble metal vias 22 extending through the thickness direction of the sheet 14.
- the noble metal vias 22 may include any suitable noble metal, such ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and/or gold.
- the vias provide good electrical conductivity, thus separating the function of electrical conductivity from the water/gas transport function provided by the chemically stable porous sheets 14.
- the de-binding and sintering protocol is selected to obtain a continuous noble metal coating on opposite major surfaces of the porous titanium layer 14, while increasing the porosity of the porous titanium sheet. This may be accomplished by using a higher de-binding temperature ramp rate and/or a lower sintering temperature.
- the relatively high de-binding ramp rate may be from 1 oC / min to 5 oC / min, for example, from 2 oC / min to 4 oC / min.
- the relatively low sintering temperature may be from 1100 oC to 1300 oC, such as from 1150 oC to 1250 oC.
- the method of forming the anode side gas diffusion layer 14 includes control of silicide formation.
- silicide phases during sintering see J. D. Bolton, M. Youseffi & B. S. Becker (1998) Silicide Phase Formation and Its Influence on Liquid Phase Sintering in 316L Stainless Steel with Elemental Silicon Additions, Powder Metallurgy 41:2, (1998) 93-101, available at https://www.tandfonline.com/doi/abs/10.1179/pom.1998.41.2.93, incorporated herein by reference in its entirety).
- silicide formation control includes using titanium powder 112 with less than 0.1 weight percent silicon (e.g., 0 to 0.01 weight percent silicon) in the powder metallurgy process used to form the anode side gas diffusion layer.
- the total or substantial absence of silicon in the titanium powder avoids or reduces formation of titanium silicide phase or phases on the surface of the anode side gas diffusion layer, which may provide undesirable surface properties for the anode side gas diffusion layer.
- silicide formation control includes using titanium powder 112 with at least 1 weight percent silicon (e.g., 1 to 10 weight percent silicon) dispersed throughout the entire die cavity in the powder metallurgy process used to form the anode side gas diffusion layer 14.
- the titanium silicide phase forms throughout the entire thickness of the anode side gas diffusion layer during sintering (e.g., liquid phase sintering), and acts as a pore former.
- the porosity of the anode side gas diffusion layer 14 is increased by intentionally generating silicide phase pore former during sintering, which leaves pores in the anode side gas diffusion layer.
- the powder metallurgical method of making a porous titanium sheet configured to function as an anode side gas diffusion layer of a proton exchange membrane (PEM) electrolyzer includes providing a mixture of titanium powder and lubricant into a die cavity, compressing the mixture of titanium powder and lubricant in the die cavity to form a green sheet, de-binding the green sheet, and sintering the green sheet to form the porous titanium sheet.
- PEM proton exchange membrane
- the method also includes providing a first mixture of a noble metal powder and lubricant into the die cavity prior to providing the mixture of titanium powder and lubricant into the die cavity, and providing a second mixture of a noble metal powder and lubricant into the die cavity after providing the mixture of titanium powder and lubricant into the die cavity. Compressing the mixture of the titanium powder and the lubricant in the die cavity occurs together with compressing the first and second mixtures of the noble metal and lubricant to form the green sheet, and the step of sintering the green sheet forms the porous titanium sheet having a noble metal coating on both major surfaces of the porous titanium sheet.
- the porous titanium layer (e.g., sheet) that is used as an anode side gas diffusion layer 14 is formed by the tape casting process.
- Figure 6 illustrates an exemplary tape casting apparatus 200 that may be used to form the anode side gas diffusion layer 14.
- the low-cost and scalable tape casting process can continuously produce large-format titanium containing tape used to form the anode side gas diffusion layers 14.
- a slip material 202 such as a mixture (e.g., slurry) of a titanium powder, a solvent, a binder and optionally one or more additional ingredients, such as a plasticizer and/or surfactant, is provided from a storage vessel, such as a fluid holding tank into a dispensing chamber 204.
- the titanium powder may comprise elemental (i.e., metal) titanium powder and/or titanium hydride (e.g., TiH2) powder.
- Titanium hydride powder may be used to lower the production cost by a lower raw material cost and less energy usage during sintering due to its exothermic reaction when undergoing Ti conversion around 600 to 800 degrees C.
- the titanium containing powder comprises a mixture of elemental titanium and titanium hydride powders, and the titanium hydride is subsequently thermally converted to elemental titanium in an exothermic reaction, such as during sintering and/or during a separate annealing step.
- titanium and titanium hydride powders with a desired particle size and distribution are blended together, and mixed with a polymeric binder, organic solvent and organic plasticizer which can be removed during a low oxygen or oxygen-free sintering process to form pores in the tape cast anode side gas diffusion layer 14.
- the binder, solvent and plasticizer may comprise polypropylene carbonate (“PPC”), methyl ethyl ketone (“MEK”), and polycarbonate (“PC”), respectively. Other suitable materials may also be used.
- PPC polypropylene carbonate
- MEK methyl ethyl ketone
- PC polycarbonate
- the slip material 202 is dispensed from the dispensing chamber 204 onto a moving tape carrier web 206.
- the tape carrier web 206 may comprise a metal (e.g., steel), glass, polymer, etc., belt that moves past a doctor blade 208.
- the slip material 202 moving on the tape carrier web 206 under the doctor blade 208 is flattened into a green titanium containing tape 210 by the doctor blade 208.
- Green titanium containing tapes 210 of various blends of powder sizes, specific content and solid ratios can be produced with slight variations of the slip material (i.e., slurry) 202 formulations.
- the tape carrier web 206 may then move the green titanium containing tape 210 through a drying chamber 212.
- the drying chamber 212 may include a heated air inlet 214 and a saturated air outlet 216.
- the heated air (or another source of heat) dries the green titanium containing tape 210, and the solvent which is evaporated from the tape 210 is removed with the air through the saturated air outlet 216.
- the dried green titanium containing tape 210 may then by cut into titanium green sheets 210S having the shape of the anode side gas diffusion layer in a cutting station 218.
- the dried green titanium containing tape 210 that has been cut into the titanium green sheets 210S is subsequently sintered in the sintering chamber 220 at a desired temperature to form the anode side gas diffusion layers 14.
- the titanium green sheets 210S are sintered in an oxygen-free or a low oxygen atmosphere at 1000 to 1100 degrees C.
- the atmosphere may comprise an inert atmosphere of any suitable inert gas, such as a noble gas, such as argon.
- the atmosphere may comprise an oxygen partial pressure of less than 0.1 atm, such as 0.0001 to 0.01 atm.
- the dried green titanium containing tape 210 may be provided from the drying chamber 212 into the cutting station 218 and the cut tape (i.e., titanium green sheets 210S) is then provided from the cutting station 218 into a sintering chamber 220 for sintering using the same tape carrier web 206.
- additional chambers such as a de-bindering chamber, may be located between the drying chamber 212 and the sintering chamber 220 if a de-bindering step which is carried out at a temperature between the drying and sintering temperatures is desired.
- the sintering chamber 220 may comprise a resistively or gas heated continuous furnace (e.g., belt furnace).
- the dried green titanium containing tape 210 i.e., the titanium green sheet 210S
- the sintering chamber 220 may comprise a rapid thermal annealing (“RTA”) apparatus (also referred to as a rapid thermal processing (“RTP”) apparatus) in which the cut dried green titanium containing tape 210 (i.e., the titanium green sheet 210S) is heated by a flash lamp or a laser beam.
- RTA rapid thermal annealing
- the green titanium containing tape 210 moves through the drying chamber 212, the cutting station 218 and the RTA apparatus on the same tape carrier web 206.
- the steps of flattening the slip material 202, drying the tape, cutting the tape and sintering the cut tape may occur continuously on the same moving tape carrier web 206.
- the sintering chamber 220 may comprise an upstream portion 220A and a downstream portion 220B which is located downstream of the upstream portion 220A with respect to the moving direction of the tape carrier web 206.
- An optional partition 220P may be provided between the upstream and the downstream portions of the sintering chamber 220.
- the upstream portion 220A may be maintained in an oxygen free or low oxygen atmosphere, such as a noble gas (e.g., argon) atmosphere.
- the downstream portion 220B may be maintained in a nitrogen containing atmosphere, such as a nitrogen gas or ammonia containing atmosphere (e.g., a low pressure or vacuum atmosphere with a nitrogen containing gas partial pressure).
- the titanium green sheet 210S may be reactively sintered in the downstream portion 220B to form a titanium nitride layer on its surface. Therefore, the titanium gas diffusion layer 14 may have a titanium nitride coating on one or both major surfaces 14A, 14B.
- the titanium nitride forms a hard, corrosion resistant and electrically conductive coating on the titanium gas diffusion layer 14. This coating improves the performance of the titanium gas diffusion layer 14.
- the noble metal (e.g., Au or Pt) corrosion resistant coating may be omitted if the titanium nitride corrosion resistant coating is formed.
- the titanium gas diffusion layer 14 formed by methods other than tape casting, such as powder metallurgy, may also be reactively sintered to form a titanium nitride coating thereon.
- the slip material 202 may be provided onto the tape carrier web 206 from the side and/or from the bottom instead of from the top as shown in Figure 6. If the slip material 202 is provided from the side, then the apparatus 200 may be referred to as a slot-die coater apparatus. If the slip material 202 is provided form the bottom, then the apparatus 200 may be referred to as a lip coater or a micro-gravure coater.
- the tape casting method may comprise mixing a titanium containing powder with binder, solvent and plasticizer to form a slip material 202, dispensing the slip material 202 onto the tape carrier web 206, flattening the slip material 202 moving on the tape carrier web 206 into a green titanium containing tape 210 using a doctor blade 208, drying the green titanium containing tape 210 in the drying chamber 212, cutting the greed titanium containing tape 210 into a first titanium green sheet 210S having a first porosity in the cutting station 218, and sintering the first green sheet 210S to form the porous titanium sheet 14.
- a sacrificial pore former material powder may be added to the slip material (i.e., slurry) 202, to allow higher sintering temperatures, thus leading to anode side gas diffusion layers 14 with higher flexural strength and toughness.
- pore former material may comprise engineered carbon powder, or spherical micron and/or sub-micron sized poly (methyl methacrylate) (“PMMA”) powder.
- PMMA methyl methacrylate
- the pore former material is removed during the sintering step to form pores in the gas diffusion layer 14.
- the porous titanium sheet gas diffusion layer 14 of Figure 3 which has a higher porosity in one portion 14A than in another portion 14B may be formed by tape casting.
- Such porous titanium sheet may be formed by forming two separate green titanium sheets 210S having different porosities.
- the different porosities may be obtained by using different titanium powder size, different solids ratios, different content of the tape material and/or pore former materials having a different volume, composition and/or size in the slip material 202.
- the two green titanium sheets 210S having different porosities are then placed in contact with each other and then sintered.
- the sintering forms the porous titanium sheet gas diffusion layer 14 of Figure 3 with a functional grading of pore sizes and microstructure.
- the tape casting method also includes placing a second titanium green sheet 210S having a second porosity different from the first porosity on the first titanium green sheet 210S prior to the sintering.
- the first and the second titanium green sheets 210S are sintered in contact with each other such that a first major side 14A of the resulting sintered porous titanium sheet 14 has a higher porosity than an opposite second major side 14B of the porous titanium sheet 14B.
- the conductive vias 22 shown in Figure 5 may be formed the tape cast gas diffusion layer 14.
- the conductive vias 22 may be formed by forming a noble metal or conductive titanium compound vias into the green and/or sintered titanium containing tape 210.
- larger titanium or titanium hydride particles and/or wires may be added to the slip material 202. The larger particles may have an average diameter that is within 20%, such as within 10% of the thickness of the porous titanium sheet 14.
- the wires may have an average length that is within 20%, such as within 10% of the thickness of the porous titanium sheet 14.
- the larger particles and/or wires are mixed with titanium or titanium hydride powder particles which have an average diameter that is less than 50% of the thickness of the porous titanium sheet 14.
- the larger particles and/or wires extend through the entire thickness of the porous titanium sheet 14 and function as the conductive vias 22.
- the thickness of the porous titanium sheet 14 is the dimension between the first major side 14A and the second major side 14A of the porous titanium sheet 14.
- the green titanium containing tape 210 may have its surface embossed (e.g., roughened or patterned) to create raised and lowered surface portions.
- the patterns may comprise dimples that are recessed into the tape surface and/or a “waffle” shaped grid which protrudes from or is recessed into the tape surface.
- the embossing of the tape may increase its surface area and improve water flow.
- the embossing e.g., surface roughening or patterning
- a noble metal coating e.g., gold or platinum group metal coating
- another corrosion inhibitor material coating may be formed on the porous titanium sheet 14 during the tape casting.
- a powder of the corrosion inhibitor material may be formed on the surface of the dried green titanium containing tape 210 prior to sintering, to sinter the corrosion inhibitor coating onto at least one surface of the porous titanium sheet 14.
- ions of a material other than titanium may be implanted into the porous titanium sheet 14 or into the dried green titanium containing tape 210.
- silicon atoms may be ion implanted into the to form the titanium silicide pore former regions described above.
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Abstract
A porous titanium sheet configured to function as an anode side gas diffusion layer of a proton exchange membrane (PEM) electrolyzer is formed by a powder technique, such as tape casting or powder metallurgy.
Description
POROUS ELECTROLYZER GAS DIFFUSION LAYER AND METHOD OF MAKING THEREOF Cross-Reference To Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63/056,820, filed on July 27, 2020, the entire contents of which are incorporated herein by reference. Field The present disclosure is directed to electrolyzers in general and to a gas diffusion layer for an electrolyzer and method of making thereof in particular. Background Proton exchange membrane (PEM) electrolyzers may be used to convert water into separate hydrogen and oxygen streams. Such PEM electrolyzers include a polymer electrolyte located between an anode electrode and a cathode electrode. Anode side and cathode side porous gas diffusion layers are located adjacent to the respective anode and cathode electrodes. Summary In one embodiment, a porous titanium sheet configured to function as an anode side gas diffusion layer of a proton exchange membrane (PEM) electrolyzer is formed by a powder technique. In one embodiment, a method comprises making a porous titanium sheet configured to function as an anode side gas diffusion layer of a proton exchange membrane (PEM) electrolyzer by a powder technique. Figures Figure 1 is a perspective cut-away view of a PEM electrolyzer. Figures 2A – 2F are side cross sectional views of steps in a powder metallurgy method of making a gas diffusion layer for a PEM electrolyzer.
Figure 3 is a perspective view of a gas diffusion layer according to an embodiment of the present disclosure. Figures 4 and 5 are another perspective views of a gas diffusion layer according to embodiments of the present disclosure. Figure 6 is side cross sectional view of a tape casting apparatus which may be used to form a gas diffusion layer according to embodiments of the present disclosure. Detailed Description Figure 1 illustrates a perspective cut-away view of a PEM electrolyzer that is described in an article by Greig Chisholm et al. “3D printed flow plates for the electrolysis of water: An economic and adaptable approach to device manufacture” Energy Environ. Sci., 2014, 7, 3026–3032. The PEM electrolyzer 1 includes an anode side flow plate 2 and cathode side flow plate 4 with fluid flow channels 6 and respective openings 8, 9, 10, a PEM polymer electrolyte 12 located between the flow plates 2, 4, an anode side gas diffusion layer 14 located between the electrolyte 12 and the anode side flow plate 2, an anode electrode 16 located between the anode side gas diffusion layer 14 and the electrolyte 12, a cathode side gas diffusion layer 18 located between the electrolyte 12 and the cathode side flow plate 4, and a cathode electrode 20 located between the cathode side gas diffusion layer 18 and the electrolyte 12. The anode side flow plate 2 may include a water inlet opening 8, an oxygen outlet opening 9 and a water flow channel (e.g. tortuous path groove) 6 connecting the water inlet opening 8 and the oxygen outlet opening 9 in the side of the flow plate 2 facing the anode side gas diffusion layer 14. The anode side gas diffusion layer 14 may comprise a porous titanium layer. The cathode side gas diffusion layer 18 may comprise a porous carbon layer. The anode electrode 16 may comprise any suitable anode catalyst, such as an iridium layer. The cathode electrode 20 may comprise any suitable cathode catalyst, such as a platinum layer. Other noble metal catalyst layers may also be used for the anode and/or cathode electrodes. The electrolyte 12 may comprise any suitable proton exchange (e.g., hydrogen ion transport) polymer membrane, such as a Nafion® membrane composed of sulfonated tetrafluoroethylene based fluoropolymer-copolymer having a formula C7HF13O5S.C2F4.
In operation, water is provided into the water flow channel 6 through the water inlet opening 8. The water flows through the water flow channel 6 and through the anode side gas diffusion layer 14 to the anode electrode 16. The water is electrochemically separated into oxygen and hydrogen at the anode electrode 16 upon an application of an external current or voltage between the anode electrode 16 and the cathode electrode 20. The oxygen diffuses back through the anode side gas diffusion layer 14 to the anode side flow plate 2 and exits the electrolyzer 1 through the oxygen outlet opening 9. The hydrogen ions diffuse through the electrolyte 12 to the cathode electrode 20 and then exit the electrolyzer 1 through the cathode side gas diffusion layer 18 and the hydrogen outlet opening 10 in the cathode side flow plate 4. A porous titanium layer (e.g., sheet) may be used as the anode side gas diffusion layer (i.e., transport layer) 14. In one embodiment, the porous titanium layer (e.g., sheet) that is used as an anode side gas diffusion layer 14 is formed by a powder process. In one embodiment, the powder process comprises tape casting. After the porous titanium sheet is sintered, it may be coated on both sides (e.g., on the anode electrode side and the flow plate side) with a conductivity enhancing and/or corrosion resistant coating, such as a platinum and/or gold coating to provide good conductivity and corrosion resistance. The coating may be formed by physical vapor deposition, such as evaporation. In another embodiment, the porous titanium layer (e.g., sheet) that is used as an anode side gas diffusion layer 14 is formed by a powder metallurgical technique, in which a titanium powder is pressed into a porous titanium sheet using compaction process. The compacted sheet is then sintered to yield a gas diffusion layer (e.g., sheet) with an established metallurgical bond. The porous titanium sheet may have a porosity between 40 and 60 percent. Figures 2A to 2F show exemplary steps in a powder metallurgy technique (e.g., a technique illustrated on azom.com (https://www.azom.com/article.aspx?ArticleID=155)) that may be used to form the porous anode side titanium gas diffusion layer. The powder metallurgy press apparatus 100 includes a chamber 101 containing an upper punch 102 and a lower punch 104 that move axially relative to a die cavity 106 located in a die 108.
The steps in the powder metallurgy compaction cycle include lowering the lower punch 104 from the elevated position to expose the die cavity 106, as shown in Figures 2A and 2B. The titanium powder 112 is mixed with a lubricant and then provided into a powder shoe 110. The powder shoe 110 containing the titanium powder 112 mixed with the lubricant moves over the die cavity to fill the die cavity with a mixture of titanium powder 112 and lubricant. After the shoe 110 is withdrawn, the top and/or bottom punches 102, 104 move relative to the die 108 to compress the titanium powder 112, as shown in Figures 2C and 2D. After compaction the top punch 102 is retracted upwards and the bottom punch 104 moves relative to the die 108 to eject the compacted green titanium sheet 114 from the die cavity 106, as shown in Figure 2E. The shoe 110 then again moves across the top surface of the die 108 where it refills the die cavity with additional titanium powder 112 and lubricant mixture and pushes the green titanium sheet 114 out of the die 108, as shown in Figure 2F. The green titanium sheet 114 may be provided onto a moving belt which moves the green titanium sheet through one or more belt furnaces. The sheet may first be annealed at a lower temperature in a de-binding process to burn out the organic lubricant (i.e., binder), followed by annealing at a high temperature to sinter the de-lubricated titanium sheet. The sintered porous titanium sheet 14 is then provided into the electrolyzer (e.g., the electrolyzer 1 of Figure 1) between the anode side flow plate 2 and the membrane – electrode assembly (i.e., the electrolyte 12 with anode electrode 16 and cathode electrode 20 located on opposite sides thereof) to function as the anode side gas diffusion layer 14. In one embodiment shown in Figure 3, a first major side 14A of the porous titanium sheet 14 has a higher porosity than an opposite second major side 14B of the porous titanium sheet 14. The first major side 14A of the porous titanium sheet 14 faces the anode side flow plate 2, and the opposite second major side 14B of the porous titanium sheet 14 faces the anode electrode 16. For example, the first major side 14A of the porous titanium 14 sheet may have the porosity which is at least 10 percent higher than the opposite second major side 14B of the porous titanium sheet 14. The first major side 14A of the porous titanium sheet may have a porosity of 40 to 50%, while the opposite second major side 14B of the porous titanium sheet may have a porosity of 50 to 60%. In one embodiment, the higher porosity on the flow
plate 2 side 14A of the porous titanium sheet 14 permits more water to enter the pores, while the lower porosity on the anode electrode 16 side 14B of the titanium sheet 14 provides an improved electrical contact with the anode electrode 16. The porosity difference may be a continuous porosity gradient in which the porosity increases continuously from the first major side 14A to the second major side 14B (i.e. between opposing major surfaces). Alternatively, the porosity may change in a stepwise fashion such that the porous titanium sheet 14 has at least first and second portions (14A, 14B) having different respective porosities from each other. To form different porosity regions, a different amount of lubricant is added to top and bottom sections of the titanium powder 112 in the die cavity 106 in a continuous gradient or in a stepwise manner. The porous titanium sheet 14 has a higher porosity in a portion 14A that is made from a powder section containing a higher lubricant concentration than in a portion 14B that is made from a powder section containing a lower lubricant concentration. The different lubricant concentration in the die cavity 106 may be formed by two or more different passes of the shoe 110 in which the titanium powder 112 to lubricant ratio is different (e.g., higher or lower) in different passes. The die cavity 106 is partially filled during the first shoe 110 pass with a first portion of the mixture of the titanium powder 112 and lubricant having a first titanium powder to lubricant ratio, and the die cavity 106 is additionally filled during the second shoe 110 pass with a second portion of the mixture of the titanium powder 112 and lubricant having a second titanium powder to lubricant ratio different from the first ratio. The lower titanium powder 112 to lubricant ratio results in a higher porosity during the de-binding anneal step. In another embodiment, a first major surface of the anode side flow plate which faces the anode side gas diffusion layer 14 contains a water flow channel groove 6, as shown in Figure 1. The first major side 14A of the porous titanium sheet 14 which faces the anode side flow plate 2 includes a groove 26 which is a substantial mirror image of the water flow channel groove 6, as shown in Figure 3. As used herein, a substantial mirror image of the water flow channel groove 26 means a shape which is a general mirror image of the water flow channel groove 6, but which may have dimensions which differ by less than 20%. In contrast, an opposite second major side 14B of the porous titanium sheet 14 which faces the anode electrode 16 has a substantially planar surface which lacks a groove 26. Such design facilitates water
flow on the flow plate 2 side 14A of the gas diffusion later 14, while maintaining a good electrical contact between the gas diffusion layer 14 and the anode electrode 16. The groove 26 in the porous titanium sheet 14 may be formed by using the upper punch 102 or the lower punch 104 in the apparatus of FIG.2A which contains a protrusion which is a mirror image of the groove 26. In another embodiment shown in Figure 4, the porous titanium sheet 14 has a bimodal distribution of pore sizes as part of the porosity network. The two modes of the pore sizes are broadly classified as micropores 15B and macropores 15A which are larger than the micropores 15B. Micropores 15B act as capillary tubes and help transport water from the groove 6 to the anode electrode (e.g., anode catalyst layer) 16, while the macropores 15A provide low flow resistive path for generated gas to leave electrocatalyst to the grove 6 to be transported by the flowing water. Pore sizes may be calculated using Young Laplace equation. In one embodiment, the micropore 15B average pore size is in the range of 1 to 5 microns and the macropore 15A average pore size is in the range of 30 to 40 microns. In another embodiment, the porous titanium sheet 14 formation in the powder press apparatus 100 of Figures 2A – 2F is carried out in an inert, low oxygen partial pressure atmosphere in the chamber 101 so that titanium is not oxidized to titanium dioxide to reduce resistive losses and avoid a fire due to titanium oxidation. The inert atmosphere may comprise any suitable inert gas, such as a noble gas, such as argon. The atmosphere may comprise an oxygen partial pressure of less than 0.1 atm, such as 0.0001 to 0.01 atm. The inert gas may be provided into the chamber 101 containing the die 108 and the punches 102, 104. Alternatively the inert gas may be provided into the die cavity as a gas blanket from an inert gas conduit after filling the die cavity with the titanium powder. In another embodiment, the porous titanium sheet 14 formation in the powder press apparatus 100 of Figures 2A – 2F is carried out with titanium alloy powders. Titanium may be alloyed with any one or more of molybdenum, vanadium, niobium, tantalum, and/or zirconium. Thus, a titanium alloy powder containing more than 50 atomic percent titanium (e.g., 60 to 99 atomic percent Ti and less than 50 atomic percent, such as 1 to 40 atomic percent molybdenum, vanadium, niobium, tantalum, and/or zirconium) may be used in the powder press apparatus. The powder particles
comprise the titanium alloy particles. Alternatively, a combination (e.g., mixture) of two powders may be used in the powder press apparatus: a titanium containing powder, such as a pure titanium powder, and an alloying element powder containing molybdenum, vanadium, niobium, tantalum, and/or zirconium. The combination of the powders contains more than 50 atomic percent titanium powder particles (e.g., 60 to 99 atomic percent Ti) and less than 50 atomic percent, such as 1 to 40 atomic percent of the alloying element powder particles. The porous titanium alloy sheet is formed during compaction in the powder press apparatus. The combination of chemical stability requirements and the processability requirements may be used to select the grade of titanium alloy. The alloy grades can be Grades 1, 2, 3, 6, 7, 9, 11, 16, 17,18, 21, 24, 26, 27, 29, 32, 36 and/or 37. In another embodiment, a noble metal coating (e.g., gold or platinum group metal coating) may be formed on the porous titanium sheet 14 during the powder metallurgy process, which increases the coating process speed and reduces the coating process cost. In this embodiment, a noble metal powder is provided into the die cavity 106 below and above the titanium powder 112, following by compressing all powders together using the punches 102, 104, as shown in Figures 2A – 2F. The different powder layers may be formed by three or more different passes of the shoe 110 in which the powder composition varies in different passes. The die cavity 106 is partially filled during the first shoe pass with a noble metal powder and lubricant mixture, then the die cavity is additionally filled with a titanium powder 112 and lubricant mixture during the second shoe pass, and finally the die cavity is filled with a noble metal powder and lubricant mixture during the third shoe pass. In one embodiment, two different shoes 110 filled with different powder may be used. A first shoe filled with the noble metal powder and lubricant mixture is used during the first and the third shoe passes. A different second shoe filled with the titanium powder and lubricant mixture is used during the second shoe pass. This forms a noble metal / titanium / noble metal powder tri-layer in the die cavity. The tri-layer is then compressed to form a porous titanium plate coated on both major surfaces by a noble metal. In another embodiment shown in Figure 5, the porous titanium sheet has inherent vias that are filled in with one or more noble metal powder to create highly conductive vias 22. In other words, the porous titanium or titanium alloy sheet 14
includes noble metal vias 22 extending through the thickness direction of the sheet 14. The noble metal vias 22 may include any suitable noble metal, such ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and/or gold. The vias provide good electrical conductivity, thus separating the function of electrical conductivity from the water/gas transport function provided by the chemically stable porous sheets 14. In another embodiment, the de-binding and sintering protocol is selected to obtain a continuous noble metal coating on opposite major surfaces of the porous titanium layer 14, while increasing the porosity of the porous titanium sheet. This may be accomplished by using a higher de-binding temperature ramp rate and/or a lower sintering temperature. In one embodiment, the relatively high de-binding ramp rate may be from 1 ºC / min to 5 ºC / min, for example, from 2 ºC / min to 4 ºC / min. In one embodiment, the relatively low sintering temperature may be from 1100 ºC to 1300 ºC, such as from 1150 ºC to 1250 ºC. In another embodiment, the method of forming the anode side gas diffusion layer 14 includes control of silicide formation. For example, some metal alloys form silicide phases during sintering (see J. D. Bolton, M. Youseffi & B. S. Becker (1998) Silicide Phase Formation and Its Influence on Liquid Phase Sintering in 316L Stainless Steel with Elemental Silicon Additions, Powder Metallurgy 41:2, (1998) 93-101, available at https://www.tandfonline.com/doi/abs/10.1179/pom.1998.41.2.93, incorporated herein by reference in its entirety). Specifically, silicon addition to 316L stainless steel causes liquid silicide phase formation during sintering, which leave large pores in the stainless steel parts after sintering is completed. In one aspect of the present embodiment, silicide formation control includes using titanium powder 112 with less than 0.1 weight percent silicon (e.g., 0 to 0.01 weight percent silicon) in the powder metallurgy process used to form the anode side gas diffusion layer. The total or substantial absence of silicon in the titanium powder avoids or reduces formation of titanium silicide phase or phases on the surface of the anode side gas diffusion layer, which may provide undesirable surface properties for the anode side gas diffusion layer.
In another aspect, silicide formation control includes using titanium powder 112 with at least 1 weight percent silicon (e.g., 1 to 10 weight percent silicon) dispersed throughout the entire die cavity in the powder metallurgy process used to form the anode side gas diffusion layer 14. In this embodiment, the titanium silicide phase forms throughout the entire thickness of the anode side gas diffusion layer during sintering (e.g., liquid phase sintering), and acts as a pore former. Thus, the porosity of the anode side gas diffusion layer 14 is increased by intentionally generating silicide phase pore former during sintering, which leaves pores in the anode side gas diffusion layer. Furthermore, since the silicide phase is distributed throughout the anode side gas diffusion layer 14, the silicide phase is not concentrated on the surface of the anode side gas diffusion layer, and undesirable surface effects are avoided or reduced. Thus, the powder metallurgical method of making a porous titanium sheet configured to function as an anode side gas diffusion layer of a proton exchange membrane (PEM) electrolyzer includes providing a mixture of titanium powder and lubricant into a die cavity, compressing the mixture of titanium powder and lubricant in the die cavity to form a green sheet, de-binding the green sheet, and sintering the green sheet to form the porous titanium sheet. In one embodiment, the method also includes providing a first mixture of a noble metal powder and lubricant into the die cavity prior to providing the mixture of titanium powder and lubricant into the die cavity, and providing a second mixture of a noble metal powder and lubricant into the die cavity after providing the mixture of titanium powder and lubricant into the die cavity. Compressing the mixture of the titanium powder and the lubricant in the die cavity occurs together with compressing the first and second mixtures of the noble metal and lubricant to form the green sheet, and the step of sintering the green sheet forms the porous titanium sheet having a noble metal coating on both major surfaces of the porous titanium sheet. In another embodiment, the porous titanium layer (e.g., sheet) that is used as an anode side gas diffusion layer 14 is formed by the tape casting process. Figure 6 illustrates an exemplary tape casting apparatus 200 that may be used to form the anode side gas diffusion layer 14. The low-cost and scalable tape casting process can
continuously produce large-format titanium containing tape used to form the anode side gas diffusion layers 14. In an embodiment tape casting process shown in Figure 6, a slip material 202, such as a mixture (e.g., slurry) of a titanium powder, a solvent, a binder and optionally one or more additional ingredients, such as a plasticizer and/or surfactant, is provided from a storage vessel, such as a fluid holding tank into a dispensing chamber 204. The titanium powder may comprise elemental (i.e., metal) titanium powder and/or titanium hydride (e.g., TiH2) powder. Titanium hydride powder may be used to lower the production cost by a lower raw material cost and less energy usage during sintering due to its exothermic reaction when undergoing Ti conversion around 600 to 800 degrees C. Thus, in one embodiment, the titanium containing powder comprises a mixture of elemental titanium and titanium hydride powders, and the titanium hydride is subsequently thermally converted to elemental titanium in an exothermic reaction, such as during sintering and/or during a separate annealing step. In one embodiment, titanium and titanium hydride powders with a desired particle size and distribution are blended together, and mixed with a polymeric binder, organic solvent and organic plasticizer which can be removed during a low oxygen or oxygen-free sintering process to form pores in the tape cast anode side gas diffusion layer 14. The binder, solvent and plasticizer may comprise polypropylene carbonate (“PPC”), methyl ethyl ketone (“MEK”), and polycarbonate (“PC”), respectively. Other suitable materials may also be used. The slip material 202 is dispensed from the dispensing chamber 204 onto a moving tape carrier web 206. The tape carrier web 206 may comprise a metal (e.g., steel), glass, polymer, etc., belt that moves past a doctor blade 208. The slip material 202 moving on the tape carrier web 206 under the doctor blade 208 is flattened into a green titanium containing tape 210 by the doctor blade 208. Green titanium containing tapes 210 of various blends of powder sizes, specific content and solid ratios can be produced with slight variations of the slip material (i.e., slurry) 202 formulations. The tape carrier web 206 may then move the green titanium containing tape 210 through a drying chamber 212. The drying chamber 212 may include a heated air inlet 214 and a saturated air outlet 216. The heated air (or another source of heat)
dries the green titanium containing tape 210, and the solvent which is evaporated from the tape 210 is removed with the air through the saturated air outlet 216. The dried green titanium containing tape 210 may then by cut into titanium green sheets 210S having the shape of the anode side gas diffusion layer in a cutting station 218. The dried green titanium containing tape 210 that has been cut into the titanium green sheets 210S is subsequently sintered in the sintering chamber 220 at a desired temperature to form the anode side gas diffusion layers 14. Preferably, the titanium green sheets 210S are sintered in an oxygen-free or a low oxygen atmosphere at 1000 to 1100 degrees C. The atmosphere may comprise an inert atmosphere of any suitable inert gas, such as a noble gas, such as argon. The atmosphere may comprise an oxygen partial pressure of less than 0.1 atm, such as 0.0001 to 0.01 atm. In one embodiment, the dried green titanium containing tape 210 may be provided from the drying chamber 212 into the cutting station 218 and the cut tape (i.e., titanium green sheets 210S) is then provided from the cutting station 218 into a sintering chamber 220 for sintering using the same tape carrier web 206. Optionally, additional chambers, such as a de-bindering chamber, may be located between the drying chamber 212 and the sintering chamber 220 if a de-bindering step which is carried out at a temperature between the drying and sintering temperatures is desired. In one embodiment, the sintering chamber 220 may comprise a resistively or gas heated continuous furnace (e.g., belt furnace). In this embodiment, the dried green titanium containing tape 210 (i.e., the titanium green sheet 210S) moves through the drying chamber 212, the cutting station 218 and the continuous furnace on the same tape carrier web 206. In another embodiment, the sintering chamber 220 may comprise a rapid thermal annealing (“RTA”) apparatus (also referred to as a rapid thermal processing (“RTP”) apparatus) in which the cut dried green titanium containing tape 210 (i.e., the titanium green sheet 210S) is heated by a flash lamp or a laser beam. In this embodiment, the green titanium containing tape 210 moves through the drying chamber 212, the cutting station 218 and the RTA apparatus on the same tape carrier web 206. Thus, the steps of flattening the slip material 202, drying the tape, cutting the tape and sintering the cut tape may occur continuously on the same moving tape carrier web 206.
In one embodiment, the sintering chamber 220 may comprise an upstream portion 220A and a downstream portion 220B which is located downstream of the upstream portion 220A with respect to the moving direction of the tape carrier web 206. An optional partition 220P may be provided between the upstream and the downstream portions of the sintering chamber 220. The upstream portion 220A may be maintained in an oxygen free or low oxygen atmosphere, such as a noble gas (e.g., argon) atmosphere. The downstream portion 220B may be maintained in a nitrogen containing atmosphere, such as a nitrogen gas or ammonia containing atmosphere (e.g., a low pressure or vacuum atmosphere with a nitrogen containing gas partial pressure). The titanium green sheet 210S may be reactively sintered in the downstream portion 220B to form a titanium nitride layer on its surface. Therefore, the titanium gas diffusion layer 14 may have a titanium nitride coating on one or both major surfaces 14A, 14B. The titanium nitride forms a hard, corrosion resistant and electrically conductive coating on the titanium gas diffusion layer 14. This coating improves the performance of the titanium gas diffusion layer 14. Furthermore, the noble metal (e.g., Au or Pt) corrosion resistant coating may be omitted if the titanium nitride corrosion resistant coating is formed. It should be noted that the titanium gas diffusion layer 14 formed by methods other than tape casting, such as powder metallurgy, may also be reactively sintered to form a titanium nitride coating thereon. In alternative embodiments, the slip material 202 may be provided onto the tape carrier web 206 from the side and/or from the bottom instead of from the top as shown in Figure 6. If the slip material 202 is provided from the side, then the apparatus 200 may be referred to as a slot-die coater apparatus. If the slip material 202 is provided form the bottom, then the apparatus 200 may be referred to as a lip coater or a micro-gravure coater. In summary, the tape casting method may comprise mixing a titanium containing powder with binder, solvent and plasticizer to form a slip material 202, dispensing the slip material 202 onto the tape carrier web 206, flattening the slip material 202 moving on the tape carrier web 206 into a green titanium containing tape 210 using a doctor blade 208, drying the green titanium containing tape 210 in the drying chamber 212, cutting the greed titanium containing tape 210 into a first titanium green sheet 210S having a first porosity in the cutting station 218, and sintering the first green sheet 210S to form the porous titanium sheet 14.
In one embodiment, a sacrificial pore former material powder may be added to the slip material (i.e., slurry) 202, to allow higher sintering temperatures, thus leading to anode side gas diffusion layers 14 with higher flexural strength and toughness. Such pore former material may comprise engineered carbon powder, or spherical micron and/or sub-micron sized poly (methyl methacrylate) (“PMMA”) powder. The pore former material is removed during the sintering step to form pores in the gas diffusion layer 14. In one embodiment, the porous titanium sheet gas diffusion layer 14 of Figure 3 which has a higher porosity in one portion 14A than in another portion 14B may be formed by tape casting. Such porous titanium sheet may be formed by forming two separate green titanium sheets 210S having different porosities. The different porosities may be obtained by using different titanium powder size, different solids ratios, different content of the tape material and/or pore former materials having a different volume, composition and/or size in the slip material 202. The two green titanium sheets 210S having different porosities are then placed in contact with each other and then sintered. The sintering forms the porous titanium sheet gas diffusion layer 14 of Figure 3 with a functional grading of pore sizes and microstructure. Thus, in this embodiment, the tape casting method also includes placing a second titanium green sheet 210S having a second porosity different from the first porosity on the first titanium green sheet 210S prior to the sintering. The first and the second titanium green sheets 210S are sintered in contact with each other such that a first major side 14A of the resulting sintered porous titanium sheet 14 has a higher porosity than an opposite second major side 14B of the porous titanium sheet 14B. In another embodiment, the conductive vias 22 shown in Figure 5 may be formed the tape cast gas diffusion layer 14. The conductive vias 22 may be formed by forming a noble metal or conductive titanium compound vias into the green and/or sintered titanium containing tape 210. Alternatively or in addition, larger titanium or titanium hydride particles and/or wires may be added to the slip material 202. The larger particles may have an average diameter that is within 20%, such as within 10% of the thickness of the porous titanium sheet 14. The wires (e.g., fibers) may have an average length that is within 20%, such as within 10% of the thickness of the porous titanium sheet 14. The larger particles and/or wires are mixed with titanium or titanium hydride powder particles which have an average diameter that is less than
50% of the thickness of the porous titanium sheet 14. The larger particles and/or wires extend through the entire thickness of the porous titanium sheet 14 and function as the conductive vias 22. As used herein, the thickness of the porous titanium sheet 14 is the dimension between the first major side 14A and the second major side 14A of the porous titanium sheet 14. In another embodiment, the green titanium containing tape 210 may have its surface embossed (e.g., roughened or patterned) to create raised and lowered surface portions. The patterns may comprise dimples that are recessed into the tape surface and/or a “waffle” shaped grid which protrudes from or is recessed into the tape surface. The embossing of the tape may increase its surface area and improve water flow. The embossing (e.g., surface roughening or patterning) may be performed by pressing a textured or patterned roller into the surface of the green titanium containing tape 210 prior to sintering, such as before or after drying the tape. In another embodiment, a noble metal coating (e.g., gold or platinum group metal coating) or another corrosion inhibitor material coating may be formed on the porous titanium sheet 14 during the tape casting. In this embodiment, a powder of the corrosion inhibitor material may be formed on the surface of the dried green titanium containing tape 210 prior to sintering, to sinter the corrosion inhibitor coating onto at least one surface of the porous titanium sheet 14. In another embodiment, ions of a material other than titanium may be implanted into the porous titanium sheet 14 or into the dried green titanium containing tape 210. For example, silicon atoms may be ion implanted into the to form the titanium silicide pore former regions described above. Although the foregoing refers to particular preferred embodiments, it will be understood that the invention is not so limited. It will occur to those of ordinary skill in the art that various modifications may be made to the disclosed embodiments and that such modifications are intended to be within the scope of the invention. All of the publications, patent applications and patents cited herein are incorporated herein by reference in their entirety.
Claims
Claims: 1. A porous titanium sheet configured to function as an anode side gas diffusion layer of a proton exchange membrane (PEM) electrolyzer, wherein the porous titanium sheet is formed by a powder technique. 2. The porous titanium sheet of claim 1, wherein a first major side of the porous titanium sheet has a higher porosity than an opposite second major side of the porous titanium sheet. 3. The porous titanium sheet of claim 2, wherein the first major side of the porous titanium sheet is configured to face an anode side flow plate, and the second major side of the porous titanium sheet is configured to face an anode electrode. 4. The porous titanium sheet of claim 2, wherein the first major side of the porous titanium sheet has the porosity which is at least 10 percent higher than the opposite second major side of the porous titanium sheet. 5. The porous titanium sheet of claim 1, wherein a first major side of the porous titanium sheet includes a groove and an opposite second major side of the porous titanium sheet has a substantially planar surface which lacks a groove. 6. The porous titanium sheet of claim 1, wherein: the porous titanium sheet contains a titanium nitride coating on at least one surface thereof; and the porous titanium sheet comprises pure titanium or an alloy of titanium containing more than 50 atomic percent titanium and less than 50 atomic percent of at least one of molybdenum, vanadium, niobium, tantalum, or zirconium. 7. The porous titanium sheet of claim 1, wherein the porous titanium sheet includes a bimodal pore size distribution comprising micropores having an average pore size in a range of 1 to 5 microns, and macropores having an average pore size in a range of 30 to 40 microns. 8. The porous titanium sheet of claim 1, further comprising conductive vias extending through the porous titanium sheet in a thickness direction of the porous titanium sheet.^ 9. A PEM electrolyzer, comprising: an anode side flow plate;
a cathode side flow plate; a PEM polymer electrolyte located between the anode side flow plate and the cathode side flow plate; the anode side gas diffusion layer comprising the porous titanium sheet of claim 1 located between the electrolyte and the anode side flow plate; an anode electrode located between the anode side gas diffusion layer and the electrolyte; a cathode side gas diffusion layer located between the electrolyte and the cathode side flow plate; and a cathode electrode located between the cathode side gas diffusion layer and the electrolyte. 10. The PEM electrolyzer of claim 9, wherein: a first major side of the porous titanium sheet has a higher porosity than an opposite second major side of the porous titanium sheet; or the first major side of the porous titanium sheet faces the anode side flow plate, and the second major side of the porous titanium sheet faces the anode electrode; or the first major side of the porous titanium sheet has the porosity which is at least 10 percent higher than the opposite second major side of the porous titanium sheet; or a first major surface of the anode side flow plate which faces the anode side gas diffusion layer contains a water flow channel groove, a first major side of the porous titanium sheet which faces the first major surface of the anode side flow plate includes a groove which is a substantial mirror image of the water flow channel groove, and an opposite second major side of the porous titanium sheet has a substantially planar surface which lacks a groove. 11. A method, comprising making a porous titanium sheet configured to function as an anode side gas diffusion layer of a proton exchange membrane (PEM) electrolyzer by a powder technique. 12. The method of claim 11, wherein the powder technique comprises a powder metallurgical technique which includes providing a mixture of titanium powder and lubricant into a die cavity, compressing the mixture of titanium powder and lubricant
in the die cavity to form a green sheet, de-binding the green sheet, and sintering the green sheet to form the porous titanium sheet. 13. The method of claim 11, wherein the powder technique comprises tape casting. 14. The method of claim 13, wherein the tape casting comprises: mixing a titanium containing powder with a binder, solvent and plasticizer to form a slip material; dispensing the slip material onto tape carrier web; flattening the slip material moving on the tape carrier web into a green titanium containing tape using a doctor blade; drying the green titanium containing tape; cutting the greed titanium containing tape into a first titanium green sheet having a first porosity; and sintering the first green sheet to form the porous titanium sheet. 15. The method of claim 14, wherein: the titanium containing powder comprises a mixture of elemental titanium and titanium hydride powders; and the titanium hydride is thermally converted to elemental titanium in an exothermic reaction. 16. The method of claim 14, further comprising adding a pore former material to the slip material and removing the pore former material during the sintering to form pores in the porous titanium sheet. 17. The method of claim 14, wherein the steps of flattening, drying, cutting and sintering occur continuously on a same moving tape carrier web. 18. The method of claim 14, further comprising placing a second titanium green sheet having a second porosity different from the first porosity on the first titanium green sheet prior to the sintering. 19. The method of claim 18, wherein:
the first and the second titanium green sheets are sintered in contact with each other such that a first major side of the porous titanium sheet has a higher porosity than an opposite second major side of the porous titanium sheet; and the first major side of the porous titanium sheet is configured to face an anode side flow plate, and the second major side of the porous titanium sheet is configured to face an anode electrode. 20. The method of claim 14, wherein: the titanium containing powder has an average diameter less than 50% of a thickness of the porous titanium sheet; the titanium containing powder is further mixed with at least one of additional titanium containing particles having an average diameter that is within 20% of the thickness of the porous titanium sheet or titanium containing wires having an average length that is within 20% of the thickness of the porous titanium sheet; and the at least one of the additional titanium containing particles or the titanium containing wires extend through an entire thickness of the porous titanium sheet and function as the conductive vias. 21. The method of claim 11, further comprising reactively sintering the porous titanium sheet in a nitrogen containing atmosphere to form a titanium nitride coating on at least one surface of the porous titanium sheet. 22. The method of claim 11, further comprising placing the porous titanium sheet into the PEM electrolyzer.
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CN114717587B (en) * | 2022-05-12 | 2023-01-31 | 清华大学 | Proton exchange membrane electrolytic cell |
WO2023222930A1 (en) * | 2022-05-17 | 2023-11-23 | Universidad Carlos Iii De Madrid | Bipolar plate of a proton-exchange membrane fuel cell and methods of manufacturing same |
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CN115090879A (en) * | 2022-07-06 | 2022-09-23 | 阳光氢能科技有限公司 | Positive electrode porous diffusion layer of PEM water electrolysis cell and preparation method and application thereof |
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